When an object moves in our visual periphery, we frequently make head and eye movements toward the object. This is done to position the fovea, the most sensitive part of the retina, on the object of interest. It has been hypothesized for some time that the superior colliculus is involved in these processes, but the physiological mechanisms are not well understood. To study the relationships between the primate superior colliculus and head and eye movements, we trained monkeys to fixate targets projected onto a tangent screen and electrically stimulated the colliculus with minute amounts of current. We selected sites from which we could evoke both eye and head movements. Since the monkeys were performing a task, we had control of their level of attentive fixation, and we were able to measure the initial positions of their eyes, head, and gaze (eye plus head). On certain trials we applied a small amount of torque to the animal's head; this approach slowed down the head on certain trials. Such data allow for a dissociation of eye, head, and gaze commands. From these approaches we discovered that the amplitude of the eye movement elicited from collicular stimulation was strongly correlated with the initial position of the eyes in the orbit (R = -0.96). In addition the amplitude of the head movement evoked by the same stimulation was also highly correlated with initial head position (R = -0.68). The contributions of both the eye and head to the gaze shift increased as their initial positions were directed toward the stimulated side. On those trials when torque was applied to the head, there was a smaller head movement elicited by the collicular stimulation. However, there was no change in the eye movement which was evoked on those trials. Thus the gaze shift produced on those trials was reduced by the amount of the reduced head movement. These results suggest that the superior colliculus drives the eye and head without determining the eye, head, or gaze amplitude. This contradicts the hypothesis that gaze amplitude is determined only by the site and parameters of stimulation. These and other data suggest that gaze is under feedback control, and the present data suggest that stimulation disrupts this feedback loop.